The permanent wave solutions now widely employed in the world are classified into the following two main groups in respect of the application method.
(1) Two-step permanent wave solution.
This solution is widely employed in professional beauty parlors and the application method comprises tightly winding on about 60 to 100 rods having diameters of about 2 to 10 mm, hair which is coated with a first solution practically containing 5 to 8% by weight of alkali thioglycolate or a modification thereof as a main component. This winding operation takes about 20 minutes. Then the wound hair is again coated with the aforesaid solution and a vinyl cap is placed on the head of the user for about 10 to 30 minutes until the solution is dissolved and softens the hair surface. Then the hair is coated with a second solution containing about 2 to 6% by weight of a strong oxidizing agent such as potassium bromate, sodium bromate, hydrogen peroxide, or the like, or with oxygen gas for about 20 to 30 minutes to fix and deodorize the dissolved and softened hair. The hair is then unwound from the rods and subjected to a warm-rinse for about 5 to 10 minutes. The hair is then coated with a hair setting lotion and wound on 30 to 60 curling rollers having diameters of 1 to 3 cm to produce large curls of 2 to 6 cm diameter according to preference. This takes about 20 minutes. The hair is then dried with hot air at a temperature of about 45.degree. C. for about 25 minutes, after which the hair is unwound from the rollers, and brushed and arranged with a comb and hairpins to complete the hair-dressing.
(2) One-step permanent wave solution.
This solution comprises almost the same composition as that of the above-mentioned first solution which dissolves and softens the hair and the application method thereof in professional beauty parlors necessarily employs the above-mentioned second solution to remove the bad smell of hydrogen sulfide and the like produced by the decomposition of the thioglycolate when applied. Otherwise, the bad smell cannot be removed at one time and it becomes necessary to fully water-rinse the hair and to subject the hair to natural deodorization in air for about four weeks. Accordingly, the conventional one-step permanent wave solutions are not true one-step ones but actually belong to the two-step solutions.
As seen from the above, the conventional two-step or one-step permanent solutions takes at least 120 minutes to complete the permanent waving and such a long application period represents a troublesome drawback.
Furthermore, the conventional permanent wave solutions generally contain 1 to 10% by weight of thioglycolic acid for dissolving and softening the hair whereby cystine and by-products of cysteine contained in the hair dissolve out and react with the second solution to inevitably produce hydrogen cyanide and other cyano compounds as pollutants which can produce chemical poisoning, such as pernicious anemia, cirrhosis of the liver or the like, and the thioglycolic acid retained in the hair renders the hair porous, coarse, non-sleek and discolored.
Permanent wave solutions are disclosed in U.S. Pat. Nos. 3,025,218 (Strain et al), 2,631,965 (Schnell) and 3,148,126 (Martin).
In U.S. Pat. No. 3,025,218, a large amount of oxy-organic acid of tartaric acid is used only for lowering the pH of the permanent wave solution but still causing the dissolved and softened hair to have a bad smell, and accordingly, a setting agent for the oxidation is required whereby the applied hair is greatly damaged. In U.S. Pat. No. 2,631,965, 1 to 10% by weight of thioglycolic acid and a large amount of oxy-organic ammonium salt are contained in alkaline aqueous solution, the hair is discolored and a bad smell is produced, and for quick deodorization in beauty parlors, it is necessary to use a setting agent for oxidation to remove the bad smell and accordingly, the solution is actually a two-step solution which damages the hair. In U.S. Pat. No. 3,148,126, the permanent wave solution contains 1 to 15% by weight of thioglycolate and monoethanolamine, and still requires a setting agent for oxidation (containing hydrogen peroxide and tartaric acid), heating at a high temperature of 150.degree. to 200.degree. F. or delivering oxygen gas under a helmet covering the scalp for quick deodorization and wave fixing. Accordingly, this permanent wave solution properly belongs to the two-step solution whereby the applied hair is greatly damaged.
The present inventor has made a special study of hair damage due to the application of the conventional permanent wave solutions and has obtained Japanese Pat. No. 299,121. He has further improved the permanent wave solution according to Japanese Pat. No. 299,121 to arrive at the present invention. The permanent wave solution of Japanese Pat. No. 299,121 is a completely one-step permanent wave solution comprising 3 to 3.5% by weight of thioglycolic acid, 0.01 to 0.03% by weight of oxy-organic acid and 1 to 2% by weight of ethyl alcohol, and caustic alkali in an amount of 0.1% or less by weight is added to adjust the pH of the solution to 7.0 to 11.0.